[jamato8]

Great review, thank you for sharing all of your hard work but then what would you do with it if you didn't share it? :^)

Xin has told me he is using fets and that is all I can go by. I actually don't care if he is using a special conductive mud as the Reference I am listening to translates my listening time into a true musical experience but this thread is about many amps and I think it is great that the quality of portable amplification has gone to such a high degree.

 

[KurtW]

Yes it's the results that count, one shouldn't get hung up on the circuit details nor the marketing hype...its the results that count.

On the other hand, engineering types are always curious. Filburt, I think you're on to something there. According to Xin:
"The chips are tiny, but they can output up to 250mA at full 6V (headroom unnecessary)! The style of this amp is totally different than all my other amps except the same small metal case used by SuperMacro-IV."

So that would rule out the chip he used in the SuperMicro-IV, and the slower AD8531 certainly is a possibility. I'm not sure why he would have given up on the SuperMicro chip, since people liked it and he would have gained something by eliminating the voltage multiplier chip.

 

[Filburt]

Well, I guess it's different from the Supermicro and Mini since he doesn't use the MAX1796 DC-DC converter, and it's different from the Supermacro since it uses SOT-23 chips, isn't user configurable, and lacks the switch functionality.

250mA and 'no headroom necessary' sounds like AD8531 to me. CMOS op-amps are the only type I'm aware of that can pull that sort of swing with that sort of output, or anywhere near that. If you look at low voltage R-R op-amps, the overwhelming majority of them are CMOS. The AD823 is one of the few low voltage r-r chips that is FET input, but it doesn't output much current and even 10mA Iout will pull it 250mV from its rails in more favourable conditions (2k ohm, near zero capacitance) than something like a headphone. I can't think of anything that isn't CMOS that comes in SOT-23 (or SC70...though these look like SOT) that meets these performance figures, or anywhere near it. IMO, the AD8615 is a better choice, though; it has lower distortion in this sort of application. Furthermore, it's already popular. Oh well, either will work OK, I guess; neither would be my first choice but I do think the switch is a bit curious.

 

[SONGsanmanwah]

Love reading you guy's first one so this thread only make me happier, subscribed!

 

[BIG POPPA]

OK guy's
If you had to rate these amps on sound alone and not on all the bells and whistles each amp may or may not have how would it be????

 

[subfocus]

Quote:

Originally Posted by HiFlight /img/forum/go_quote.gif My LE was running the OPA2134 in L&R, with single HA5002 buffers. 3/4 is the LMH6643 (buffers bypassed) The 2134/5002 is a very synergistic combination. This current configuration is the only one that has thus far completely satisfied me. Very difficult to differentiate from the 2 References that we had available for comparison when all switch settings are set to default. BTW, my LE has probably accumulated around 600 hours of use to date. It does sound fuller than my Micro, but mine is one of the originals, with no update tweaks at all. The latest Micro does have a larger, airier soundfield. I think this LE combo sounds every bit as good as my SM-IV did. Unfortunately, it is still at Dr Xin's for repair, so I cannot compare them side-by-side at this time.

Thanks for the info Ron . I've been aware of your considerable experience with op-amp rolling the SM's from your posts on Dr Xin's website , so to hear your (and others) high praise for this latest configuration is very interesting indeed.

 

[lerio]

Quote:

Originally Posted by mrarroyo /img/forum/go_quote.gif

Gorgeous

Can i ask you why no Bithead here and on first review of Amp ?

 

[Skylab]

GREAT review, guys. I have been eclipsed! You guys are now kings of the portable amp review hill

Very nice work. We have some small differences of opinion, which is excellent - gives the head-fi community different data-points.

 

[jamato8]

I have worked with tubes much of the time in the audio world and that is what I love to play with so my expderience with chips is much less. I remember now talking with Xin and what he said about the chip. FET does distinguish the chip/chips he is using and the quality. Beyond that I would let Xin say on his site whatever he wants.

 

[HiFlight]

I am preparing my take on the amps and will send it to Miguel for adding to the review. In short, I pretty well concur with the way the amps are rated. I would put the Dared tube amp right up there, probably in the top 3 or 4, but it can hardly be considered a portable amp.

I should have gotten my feedback to Miguel earlier, but had some other drains on my free time in the last few days.

It is significant to note that there were no BAD amps in the lot. Even the cheapies are an improvement over the meager output from most players.

For someone on a limited budget, any one of them will put a smile on your face.

I did note that how I would rank the amps depends almost entirely on which headphone that I am using. Some sounded better with one particular phone, while others sounded better with a different phone. I will try to qualify that in my review.

 

[DBrim]

I can't wait to see what the Move is like after burn-in! (or maybe I can, to give my wallet a bit more time to recover)

 

[Filburt]

Quote:

Originally Posted by jamato8 /img/forum/go_quote.gif I have worked with tubes much of the time in the audio world and that is what I love to play with so my expderience with chips is much less. I remember now talking with Xin and what he said about the chip. FET does distinguish the chip/chips he is using and the quality. Beyond that I would let Xin say on his site whatever he wants.

FET-Input R-R op-amps aren't particularly common, and I've never seen one that outputs 250mA. Xin's description points heavily towards CMOS op-amps and, honestly, the chips in that picture look like AD8615s (which do 150mA, but they're what are used in the Supermicro so maybe it's what he had lying around).

 

[slwiser]

Quote:

Originally Posted by Skylab /img/forum/go_quote.gif GREAT review, guys. I have been eclipsed! You guys are now kings of the portable amp review hill Very nice work. We have some small differences of opinion, which is excellent - gives the head-fi community different data-points.

Skylab,,,not eclipsed but supplemented...yours stands along side this review in helping people understand how these amps sound.

 

[jamato8]

Quote:

Originally Posted by Filburt /img/forum/go_quote.gif FET-Input R-R op-amps aren't particularly common, and I've never seen one that outputs 250mA. Xin's description points heavily towards CMOS op-amps and, honestly, the chips in that picture look like AD8615s (which do 150mA, but they're what are used in the Supermicro so maybe it's what he had lying around).

Xin has found some that put out more current than most people know about with lower input requirements. These chips are not what people are used to. I have seen the volumes of information Xin has studied about these and all the volumes of information on the different chips and it is no wonder he is taking so long. The volume of information he has pulled together is huge.

 

[Filburt]

Quote:

Originally Posted by jamato8 /img/forum/go_quote.gif Xin has found some that put out more current than most people know about with lower input requirements. These chips are not what people are used to. I have seen the volumes of information Xin has studied about these and all the volumes of information on the different chips and it is no wonder he is taking so long. The volume of information he has pulled together is huge.

Okay. Can you link me to some of this information? I'm a little surprised that I haven't heard of a 250mA output, R-R FET Input op-amp that runs at 6V and comes in SOT-23, considering I keep track of these things pretty closely, but maybe you can point me towards it. Otherwise, I think my inference of a CMOS op-amp really is pretty reasonable, given the information available.